University of Wisconsin-Madison undergraduate students with Randy Jackson at the GLBRC plots at Arlington. Photo: John Greenler/Great Lakes Bioenergy Research Center

Water Resources Research

WRI Fuels Research on the Ecological Impacts of Biofuel Cultivation3/21/2012

By Aaron R. Conklin

At the Great Lakes Research Center’s research plots in Arlington, Wis., a key part of the biofuel industry’s future is taking shape, one model cropping system at a time.

Or, more accurately, through eight different model cropping systems, planted across a gradient of diverse ecosystems.

Successful biofuel (read: ethanol) crops require a high yield—hence the industry’s current preference for continuous corn, a crop with routinely spectacular yields. But while corn has obvious yield advantages, a lack of crop diversity also carries some significant ecological drawbacks for both soil and groundwater, which has led farmers and researchers to explore other options, from switchgrass to leaves from certain types of hybrid trees.

Since 2008, a team of researchers led by Randy Jackson, a UW-Madison associate professor of grassland ecology, has been assessing the characteristics of these different types of crops in the hopes of developing a database of information to guide future cropping efforts.

A group led by Anita Thompson, a UW-Madison associate professor of biological systems engineering, is working with Jackson to examine and evaluate the groundwater quantity and quality in five of the eight systems at the research center: continuous corn; switchgrass; hybrid poplar trees; a mix of corn, soybean and canola; and, finally, Miscanthus x giganteus, a tall-growing tropical grass with invasive properties. The Water Resources Institute provided funding for the project.

Every few weeks, Thompson’s crew heads out to Arlington to collect leachate water out of tube lysimeters and measure their findings. Through leachate volumes and levels of nitrogen, phosphorous and organic carbon Thompson reveal truths about how each cropping system contributes to groundwater recharge, the process through which surface water becomes groundwater.

Despite pressure from several camps in the biofuel industry, the ultimate goal of Jackson and Thompson’s research isn’t to rank cropping systems.

“It isn’t our goal to say that this cropping system is better than this other one,” said Thompson.

“What we’re really looking for is a better understanding of the complete profile, so farmers and policy makers can make better-informed decisions.”

Groundwater quality and quantity are critical in a cropping system’s ecosystems service model, which is what makes Thompson’s efforts so important.

“Some of what we’re discovering comes down to the characteristics of the plants,” said Thompson.

“How deep do the roots penetrate? Crops without a lot of ground cover have more potential for runoff. Those with more dense vegetation tend to absorb water better.”

The data Thompson’s compiling will eventually be combined with regional water quality and quantity data to further develop, parameterize and validate a new biogeophysical hydrology model developed by her project collaborators at Michigan State University, where these same model cropping systems are being duplicated. Researchers hope the model can be used to explore the implications of climate change and biofuel-based land use changes for Great Lakes Basin water quantity and quality.

Thompson’s part of the project is still in its earliest phases and her group is still another full growing season away from generating their first round of meaningful results. That said, small discoveries are beginning to emerge. Like the fact that during the first year nitrate loads in leachate were significantly higher for continuous corn than for switchgrass.

“Of course, that also could be due to differences in fertilizer,” cautioned Thompson. “Long-term monitoring is what’s really important here. That’s what’s going to help us determine the sustainability of these cropping systems. We’re just looking at one piece of the picture.”